biotransformation


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biotransformation

 [bi″o-trans″for-ma´shun]
the series of chemical alterations of a compound (e.g., a drug) occurring within the body, as by enzymatic activity.

bi·o·trans·for·ma·tion

(bī'ō-trans'fōr-mā'shŭn),
The conversion of molecules from one form to another within an organism, often associated with change (increase, decrease, or little change) in pharmacologic activity; refers especially to drugs and other xenobiotics.
Synonym(s): biodegradation

biotransformation

/bio·trans·for·ma·tion/ (-trans″for-ma´shun) the series of chemical alterations of a compound (e.g., a drug) occurring within the body, as by enzymatic activity.

biotransformation

(bī′ō-trăns′fər-mā′shən)
n.
Chemical alteration of a substance within the body, as by the action of enzymes.

biotransformation

[-trans′fôrmā′shən]
Etymology: Gk, bios + L, trans, across, formare, to form
the chemical changes a substance undergoes in the body, such as by the action of enzymes. See also metabolic.

biotransformation

Biochemistry
Bioconversion, see there.
 
Metabolism
A series of chemical changes in a compound (e.g., a drug), which occur within the body (e.g., by enzymatic activity).
 
Pharmacology
Drug metabolism, see there.
 
Physiology
Metabolism, see there.

therapeutic drug monitoring

Clinical pharmacology The regular measurement of serum levels of drugs requiring close 'titration' of doses in order to ensure that there are sufficient levels in the blood to be therapeutically effective, while avoiding potentially toxic excess; drug concentration in vivo is a function of multiple factors Common TDM drugs Carbamazepine, digoxin, gentamycin, procainamide, phenobarbital, phenytoin, theophylline, tobramycin, valproic acid, vancomycin
Therapeutic drug levels in vivo–factors involved
Patient compliance  Ingestion of drug in the doses prescribed
Bioavailability Access to circulation, interaction with cognate receptor(s); ionized and 'free', or bound to a carrier molecule, often albumin
Pharmacokinetics Drug equilibrium requires 4-6 half-lives of drug clearance (a period of time for1/2 of the drug to 'clear', either through metabolism or excretion, multiplied by 4-6); the drug is affected by
Interaction with foods or other drugs at the site of absorption, eg tetracycline binding to cations or chelation with binding resins, eg bile acid-binding cholestyramine that also sequesters warfarin, thyroxine and digitoxin or interactions of various drugs with each other, eg digitalis with quinidine resulting in a 3-fold ↓ in digitalis clearance
Absorption may be changed by GI hypermotility or large molecule size
Lipid solubility, which affects the volume of distribution; highly lipid-soluble substances have high affinity for adipose tissue and a low tendency to remain in the vascular compartment, see Volume of distribution.
Biotransformation, with 'first pass' elimination by hepatic metabolism, in which polar groups are introduced into relatively insoluble molecules by oxidation, reduction or hydrolysis; for elimination, lipid-soluble drugs require the 'solubility' steps of glucuronidation or sulfatation in the liver; water-soluble molecules are eliminated directly via the kidneys, weak acidic drugs are eliminated by active tubular secretion that may be altered by therapy with methotrexate, penicillin, probenecid, salicylates, phenylbutazone and thiazide diuretics
First order kinetics Drug elimination is proportional to its concentration
Zero order kinetics Drug elimination is independent of the drug's concentration
Physiological factors
Age Lower doses are required in both infants and the elderly, in the former because the metabolic machinery is not fully operational, in the latter because the machinery is decaying, with ↓ cardiac and renal function, enzyme activity, density of receptors on the cell surfaces and ↓ albumin, the major drug transporting molecule
Enzyme induction, which is involved in a drug's metabolism may reduce the drug's activity; enzyme-inducing drugs include barbiturates, carbamazepine, glutethimide, phenytoin, primidone, rifampicin
Enzyme inhibition, which is involved in drug metabolism, resulting in ↑ drug activity, prolonging the action of various drugs, including chloramphenicol, cimetidine, disulfiram (Antabuse), isoniazid, methyldopa, metronidazole, phenylbutazone and sulfonamides
Genetic factors play an as yet poorly defined role in therapeutic drug monitoring, as is the case of the poor ability of some racial groups to acetylate drugs
Concomitant disease, ie whether there are underlying conditions that may affect drug distribution or metabolism, eg renal disease with ↓ clearance and ↑ drug levels, or hepatic disease, in which there is ↓ albumin production and ↓ enzyme activity resulting in a functional ↑ in drug levels, due to ↓ availability of drug-carrying proteins

bi·o·trans·for·ma·tion

(bī'ō-trans'fŏr-mā'shŭn)
The conversion of molecules from one form to another within an organism, often associated with change in pharmacologic activity; refers especially to drugs and other xenobiotics.
Synonym(s): biodegradation.

biotransformation

see BIOCONVERSION.

biotransformation

body conversion of a drug to permit or enhance its pharmacological activity

bi·o·trans·for·ma·tion

(bī'ō-trans'fŏr-mā'shŭn)
The conversion of molecules from one form to another within an organism, often associated with change in pharmacologic activity.

biotransformation,

n the chemical and physical changes produced in drugs after they enter the body (e.g., hydrolysis, conjugation).

biotransformation

the series of chemical alterations of a compound (e.g. a drug) occurring within the body, as by enzymatic activity. The metabolism of a drug may produce products that have different effects to those of the parent drug. This biotransformation may differ markedly between animal species and affect the dose rate to be used, or the usefulness of the drug.

neonatal biotransformation
is marked by a deficiency of some enzymes necessary for the biotransformation of drugs.
References in periodicals archive ?
On a etudie la biotransformation du chlorophenol-2 (cp-2) et du chlorophenol-4 (cp-4) en presence de phenol par Pseudomonas putida (ATCC 49451).
By further data evaluation obtained with the different Chelidonii herba extracts biological processes associated with liver toxicities and biotransformation were analyzed.
sulfhydryl-dependent Biotransformation and Macromolecular Binding of 1,2-Dibromo-2,4-Dicyanobutane in blood".
As biotransformation pathways are explored, Isentris also informs scientists if there are additional toxic, physicochemical, or biological properties known about the metabolites and their intermediates.
1999), there is interest in developing remedial approaches for degrading PAHs in polluted environments through PAH biotransformation by microorganisms.
The Fenholloway's andro, however, doesn't come out of any bottle but arises from the biotransformation of pollutants.
Understanding the sources, distribution and fate of contaminants in the marine environment as well as their bioavailability, bioaccumulation, biotransformation and effects on marine organisms are major components of the research effort of the Marine Chemistry Section at the Bedford Institute of Oceanography (BIO).
Cytochrome P450 is a family of isozymes responsible for the biotransformation of several drugs.
The half-life of mephenytoin is about 7 hours with biotransformation yielding an active metabolite, nirvanol, which has its own half-life of 95-144 hours.
The sign, I realize, is equally applicable to her "self" as well - a biotransformation ever in process, ever performing a series of mutual interactions, moving into a future that little boy in the library couldn't even imagine.
Overall, the data suggests that these poly-phenols may play a dual protective effect - by reducing the bioavailability of carcinogens and by interfering with their biotransformation in the liver.
It also addresses the structures of the toxins and the features which determine both the distribution of toxic materials among the organs of intoxicated species and the stability, disposition, and biotransformation of those toxins.